The ?-Sn/Ge(111) surface is a prototypical system where the ground state depends on the interplay between lattice and electron dynamics. This surface is characterized by Sn adatoms regularly located on one out of three T4 sites of the bulk terminated Ge(111) surface. We present a pump-probe VUV-IR photoemission study of the temporal dynamics ( 0 - 20 ps) of the Sn 4d core level spectra under optical excitation (IR 800 nm or 2 ?m). The aim is to unveil the complex electron-lattice coupling mechanism involved in the ?-Sn/Ge(111) (?3×?3)R30°<->3×3 surface phase transition.The photoemission measurements were done at the CELIA facility using the 27th and 29th harmonic of the laser beam produced by the AURORE apparatus. In Fig. 1 a typical photoemission spectrum collected on the ?-Sn/Ge(111) is reported. The Sn 4d core level is characterized by two distinct components as previously reported [2]. These components are assigned to two non-equivalent Sn adatoms where empty and filled surface electronic states are mainly located. The intensity of the Sn 4d components shows different time evolution when the sample is excited by 2 ?m or 800 nm radiation, pointing to different excitation mechanism for the two wavelengths. [1] J. M. Carpinelli, et al. Phys. Rev. Lett. 1997, 79, 2859 [2] J. Avila, et al. Phys Rev. Lett. 1999, 82, 442; R. I. G. Uhrberg, et al. Phys. Rev. Lett. 2000, 85, 1036; Le Lay et al. Appl. Surf. Sci. 1998, 123,
Ultrafast photoemission spectroscopy study of the electron-lattice coupling in the 2D metallic system alpha-Sn/Ge(111)
2015
Abstract
The ?-Sn/Ge(111) surface is a prototypical system where the ground state depends on the interplay between lattice and electron dynamics. This surface is characterized by Sn adatoms regularly located on one out of three T4 sites of the bulk terminated Ge(111) surface. We present a pump-probe VUV-IR photoemission study of the temporal dynamics ( 0 - 20 ps) of the Sn 4d core level spectra under optical excitation (IR 800 nm or 2 ?m). The aim is to unveil the complex electron-lattice coupling mechanism involved in the ?-Sn/Ge(111) (?3×?3)R30°<->3×3 surface phase transition.The photoemission measurements were done at the CELIA facility using the 27th and 29th harmonic of the laser beam produced by the AURORE apparatus. In Fig. 1 a typical photoemission spectrum collected on the ?-Sn/Ge(111) is reported. The Sn 4d core level is characterized by two distinct components as previously reported [2]. These components are assigned to two non-equivalent Sn adatoms where empty and filled surface electronic states are mainly located. The intensity of the Sn 4d components shows different time evolution when the sample is excited by 2 ?m or 800 nm radiation, pointing to different excitation mechanism for the two wavelengths. [1] J. M. Carpinelli, et al. Phys. Rev. Lett. 1997, 79, 2859 [2] J. Avila, et al. Phys Rev. Lett. 1999, 82, 442; R. I. G. Uhrberg, et al. Phys. Rev. Lett. 2000, 85, 1036; Le Lay et al. Appl. Surf. Sci. 1998, 123,I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
